Modelling and simulation of the source term for a sodium cooled fast reactor under hypothetical severe accident conditions; Final report of a coordinated research project

Arokiaswamy, J. A.*; Batra, C.*; Chang, J. E.*; Garcia, M.*; Herranz, L. E.*; Klimonov, I. A.*; Kriventsev, V.*; Li, S.*; Liegeard, C.*; Mahanes, J.*; et al.

IAEA-TECDOC-2006, 380 Pages, 2022/00

https://www.iaea.org/publications/15086/modelling-and-simulation-of-the-source-term-for-a-sodium-cooled-fast-reactor-under-hypothetical-severe-accident-conditions

The IAEA coordinated research project on "Radioactive Release from the Prototype Sodium Cooled Fast Reactor under Severe Accident Conditions" was devoted to realistic numerical simulation of fission products and fuel particles inventory inside the reference sodium cooled fast reactor volumes under severe accident conditions at different time scales. The scope of analysis was divided into three parts, defined as three work packages (WPs): (1) in-vessel source term estimation; (2) primary system/containment system interface source term estimation; and, (3) in-containment phenomenology analysis. Comparison of the results obtained in WP-1 indicates that the release fractions of noble gases and cesium radionuclides, and fractions of radionuclides released to the cover gas are in a good agreement. In the analysis using a common pressure history in WP-2, the results were in good agreement indicating that the accuracy of the analysis method of each institution is almost the same. The standalone case, which uses a set of pre-defined release fractions, was defined for WP-3 which enables to decouple this part of analysis from previous WPs. There is broad consensus among the predicted results by all the participants in WP-3.

Benchmark analyses on the control rod withdrawal tests performed during the PHNIX end-of-life experiments

Monti, S.*; Toti, A.*; Stanculescu, A.*; Pascal, V.*; Fontaine, B.*; Herrenschmidt, A.*; Prulhiere, G.*; Vanier, M.*; Varaine, F.*; Vasile, A.*; et al.

IAEA-TECDOC-1742, 247 Pages, 2014/06

http://www-pub.iaea.org/books/IAEABooks/10745/Benchmark-Analyses-on-the-Control-Rod-Withdrawal-Tests-Performed-during-the-PHNIX-End-of-Life-Experiments

http://www-pub.iaea.org/MTCD/Publications/PDF/TE-1742_web.pdf

A model of turbulence based on a new formulation of the turbulent Reynolds number

Kriventsev, V.; Ninokata, Hisashi; Yamaguchi, Akira; Ohshima, Hiroyuki

Journal of Fluid Mechanics, 0 Pages, 2003/12

A new model of turbulence is proposed for solving of Reynolds equations for fully-developed flow in a wall-bounded straight channelof arbitrary shape. The main idea of Multi-Scale Viscosity(MSV) model can be expressed in the followingphenomenological rule:A local deformation of axial velocity can generate the turbulence with theintensity that keeps the value of local turbulent Reynoldsnumber below some critical one. Therefore, in MSV, the only empirical parameter is the critical Reynolds number. The turbulent Revnolds numberis defined as Re = K/W, where K is kinetic energy and W is the work of friction/dissipation forces. MSV has been applied to the basic channel flows such as a circulartube, an infinitive plane chanael and an annulus. Calculated velocity profiles are in a good agreementwith expe

Numerical Prediction of Secondary Flows in Complex Areas Using Concept of Local Turbulent Reynolds Number

Ohshima, Hiroyuki; Kriventsev, V.; Yamaguchi, Akira; Ninokata, Hisashi

Journal of Nuclear Science and Technology, 40(9), p.655 - 663, 2003/00

https://doi.org/10.3327/jnst.40.655

A new model of turbulence is proposed for the estimation of Reynolds stresses in turbulent fully-developed flow in a wall-bounded straight channel of an arbitrary shape. The main idea of a Multi-Scale Viscosity (MSV) model can be expressed in the following phenomenological rule: A local deformation of axial velocity can generate the turbulence with the intensity that keeps the value of the local turbulent Reynolds number below some critical one. Therefore, in MSV, the only empirical parameter is the critical Reynolds number. MSV has been verified on the pipe flow and applied to simulation of turbulence-driven secondary flow in elementary cell of the infinitive hexagonal rod array. Since MSV can predict turbulent viscosity anisotropy in directions normal and parallel to the wall, it is capable to calculate secondary flows in the cross-section of the rod bundle. Calculations have shown that maximal intensity of secondary flow is about 1% of the mean axial velocity for the low-Re flo

MSV:Multi-Scaler Viscosity Model of Turbulence

Kriventsev, V.

JNC TN9400 2001-053, 38 Pages, 2001/04

JNC-TN9400-2001-053.pdf:1.31MB

Multi-Scale Viscosity (MSV) model is proposed for estimation of the Reynolds stresses in turbulent fully-developed flow in a wall-bounded straight channel of an arbitrary shape. We assume that flow in an "ideal" channel is always stable, i.e.laminar, but turbulence is developing process of external perturbations cased by wall roughness and other factors. We also assume that real flows are always affected by perturbations of any scale lower than the size of the channel. The turbulence can be modeled in form of internal or "turbulent" viscosity increase. The main idea of MSV can be expressed in the following phenomenological rule: A local deformation of axial velocity can generate the turbulence with the intensity that keeps the value of local turbulent Reynolds number below some critical value. Here, local turbulent Reynolds number can be defined in two different ways: (1)as a product of value of axial velocity deformation for a given scale and generic length of this scale divided by accumulated value of laminar and turbulent viscosity of lower scales (2)as a ratio of the difference between total kinetic energy and "flat-profile" kinetic energy to the work of friction forces In MSV, the only empirical parameter is the critical Reynolds number that is estimated to be around 100 in the former case and about 8.33 in the later. MSV model has been applied to the fully-developed turbulent flows in straight channels such as a circular tube and annular channel. Friction factor and velocity profiles predicted with MSV are in a good agreement with numerous experimental data. The MSV model can be classified as "zero-order" integral model of turbulence. Because of simplicity, MSV can be easily implemented for calculation of fuIly-developed turbulent flows in straight channels of arbitrary shapes including fuel assemblies of nuclear reactors. The intent of this report is to summarize the progress made in the development of the model of turbulence. Since the final ...

Discretization of Convection-Diffusion Equations With Finite; Difference Scheme Derived From Simplified Analytical Solutions

Kriventsev, V.

JNC TN9400 2000-094, 35 Pages, 2000/09

JNC-TN9400-2000-094.pdf:1.1MB

Most of thermal hydraulic processes in nuclear engineering can be described by general convection-diffusion equations that are often can be simulated numerically with finite-difference method(FDM). An effective scheme for finite-difference discretization of such equations is presented in this report. The derivation of this scheme is based on analytical solutions of a simplified one-dimensional equation written for every control volume of the finite-difference mesh. These analytical solutions are constructed using linearized representations of both diffusion coefficient and source ter. As a result, the Efficient Finite-Differencing (EFD) scheme makes it possible to significantly improve the accuracy of numerical method even using mesh systems with fewer grid nodes that, in turn, allows to speed-up numerical simulation. EFD has been carefully verified on the series of sample problems for which either analytical or very precise numerical solutions can be found. EFD has been compared with other popular FDM schemes including novel, accurate (as well as sophisticated) methods. Among the methods compared were well-known central difference scheme, upwind scheme, exponential differencing and hybrid schemes of Spalding. Also, newly developed finite-difference schemes, such as the quadratic upstream (QUICK) scheme of Leonard, the locally analytic differencing(LOAD) scheme of Wong and Raithby, the flux-spline scheme proposed by Varejago and Patankar as well as the latest LENS discretization of Sakai have been compared. Detailed results of this comparison are given in this report. These tests have shown a high efficiency of the EFD scheme. For most of sample problems considered EFD has demonstrated the numerical error that appeared to be in orders of magnitude lower than that of other discretization methods. 0r, in other words, EFD has predicted numerical solution with the same given numerical error but using much fewer grid nodes. In this report, the detailed ....